1. Field of the Invention
The present invention relates to a magnetic-shielding sheet.
2. Description of the Prior Art
Precise electric instruments, such as those for measurement frequently cause error in measurement value or erroneous operation when exposed to leakage flux from household electric appliances, office automation apparatus, building steel frames, etc. Also terrestrial magnetism may affect adversely precise electrical instruments. Thus for example, countermeasure is tentatively taken that a measurement room in which precise electrical instruments are disposed is enclosed with magnetic shielding material for protecting them against an external magnetic field. As such magnetic-shielding material are used silicon steel sheets or permalloy. These however are disadvantageous in having so poor of a magnetic-shielding ability that they are required to be processed into considerably thick sheets for use, reflecting on inconvenience and uneconomy.
Attention is being paid to amorphous alloys useful as various functional materials, which have distinguishable chemical and mechanical properties from those of crystalline alloys. Above all, iron- or cobalt-based amorphous alloy does not have crystal anisotropy, and exhibits greatly superior soft magnetic properties associated with it, i.e. very small coercive force and high magnetic permeability. Thus it is promising to be put into practice by the utilization of these properties.
On the other hand, amorphous alloys are usually available in the form of ribbon (several tens .mu.m in thickness and 100 mm in width), which must be cut into pieces and laminated to be processed into sheets of desired dimensions. In this processing, cutting may be accompanied by occasional damage, and lamination presents problems of superposition and bonding. Besides, a desired thickness is obtainable only by laminating a number of layers, thus with many processes, reflecting unfavorably on producibility.